Biodegradable composition for detecting surface discontinuities

ABSTRACT

A water washable, non-gelling colored liquid penetrant consisting essentially of a methyl ester of a fatty acid, a nonionic surfactant and a fluorescent dye, the methyl ester and the nonionic surfactant used being readily biodegradable and thereby rendering the penetrant as a whole non-polluting when subjected, without prior treatment, to the consuming action of microorganisms.

es H91 Graham et al.

[ Feb. 13, 1973 BIODEGRADABLE COMPOSITION FOR DETECTHNG SURFACE DISCONTINUITIES Inventors: Bruce C. Graham, Arlington Heights; llmars Z. Dukats, Park Ridge, both of I11.

Assignee: Magnaflux Corporation, Chicago,

Filed: April 1, 1971 Appl. No.: 130,537

US. Cl ..252/301.2 P, 252/408, 250/71 T lint. C1. .l ..C09k l/02, G01n 21/16 Field of Search ..252/408, 301.2 P, 301.2 R;

[56] References Cited UNITED STATES PATENTS 2,871,697 2/1959 Sockman ..252/30l.2 P

Primary ExaminerRobert D. Edmonds Attorney-Hill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A water washable, non-gelling colored liquid penetrant consisting essentially of a methyl ester of a fatty acid, a nonionic surfactant and a fluorescent dye, V

7 Claims, No Drawings BIODEGRADABLE COMPOSITION FOR DETECTING SURFACE DISCONTINUITIES CROSS-REFERENCES TO RELATED APPLICATIONS Reference is made to the commonly owned application of Adolf Mlot-Fijalkowski, Ser. No. 26,107, filed Apr. 6, l970, entitled Method of and Composition for Detecting Surface Discontinuities.

SUMMARY OF THE INVENTION This invention relates to a water washable, nongelling type of colored liquid penetrant and to a method of using the same for detecting the presence of surface discontinuities in solid surfaces. Our preferred 7 liquid penetrant testing composition is one that is readily biodegradable so that the spent penetrant composition without prior treatment can be disposed of without danger of causing pollution. Microorganisms normally present in the ground, streams or other bodies of water into which the spent penetrant composition is wasted quickly consume substantially all of the waste penetrant composition.

In order to accomplish the desired high degree of biodegradability of our penetrant composition, it is preferable to avoid the use of the usual relatively difficulty biodegradable aromatic hydrocarbon compounds, such as an alkylated benzene and particularly those containing branched hydrocarbon chains, and to use, instead, as the liquid vehicle for the fluorescent dye a readily biodegradable methyl ester of a C -C fatty acid, and a biodegradable ethoxylated series of nonionic surfactants consisting of ethoxylates of isomeric secondary linear alcohols. The linear hydrophobic portion of such nonionic surfactants is a mixture of C -C linear chains, while the hydrophylic portion is a polyoxyethylene chain randomly attached to the linear aliphatic chain through an ether (O) linkage. Both the linear alcohol hydrophobic portion and the polyoxyethylene portion are capable of being effectively consumed by microorganisms.

Mixtures of these nonionics of differing molecular weights that are water soluble and non-gel forming, are suitable for use in our penetrant testing composition.

Less preferred nonionic surfactants are represented by the reaction products or adducts of ethylene oxide with nonyl or octyl phenol in a molar ratio of at least 10 to l, with the average length of the hydrophylic polyoxyethylene chain preferably l2 oxyethylene units.

These adducts are not preferred since the presence of the benzene ring renders then less easily biodegradable than the ethoxylated alcohols previously mentioned, but if the side chains contain at least 6 oxyethylene units the adduct is relatively easily biodegradable.

While no coupler is required to render our liquid penetrant composition washable and therefore easily removed by water alone, various couplers can be used in relatively small proportions, such as dipropylene glycol or other glycol type coupler, or benzyl alcohol.

The major component of the liquid penetrant composition of ourinvention is, as previously stated, a methyl ester of a fatty acid that is readily biodegradable. Satisfactory embodiments of such methyl esters of fatty acids are available under the names Methyl Lardate Base ML; Methyl Sperm; and Methyl Sperm 40. Suitable methyl esters are methyl esters of fatty acids of between l6 and 24 C-atoms and preferably of from 16 to 18 C-atoms (both inclusive) fatty acids, such as those that are derivable from lard.

Typical specifications of methyl esters that are satisfactory for use as the principal liquid vehicle of our penetrant composition will be given hereinafter. The methyl esters are not employed as surfactants, but in combination with the previously mentioned nonionic surfactants constitute the entire liquid vehicle of our penetrant composition.

It is therefore an important object of this invention to provide a liquid fluorescent penetrant the major components of which are readily biodegradable so that upon disposal of the liquid penetrant waste into sewer systems, streams, rivers and other bodies of water, the waste penetrant is quickly consumed by microorganisms instead of causing pollution of the ecology.

Another important object of this invention is to replace the less readily biodegradable or nonbiodegradable liquid penetrant compositions of the prior art by a liquid penetrant composition that is readily biodegradable when in its spent form, that is, following its use as a penetrant in admixture with water rinsings.

Another important object of this invention is to provide colored liquid penetrant compositions that are of relatively low viscosity, that have desirable penetrating qualities without requiring admixture with a light oily type of solvent or extender and that have high flash points and are non-corrosive, clear and stable solutions.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain preferred embodiments thereof.

DETAILED DESCRIPTION OF THE INVENTION The colored liquid penetrant composition of our invention comprises a water-washable, non-gelling colored liquid composition consisting essentially of a methyl ester of a fatty acid, a nonionic surfactant and preferably, a fluorescent dye dissolved in the liquid vehicle. The methyl ester and the nonionic surfactant used are both readily biodegradable and thereby render the penetrant, as a whole, non-polluting when subjected, without prior treatment, to the consuming action of microorganisms naturally present in the environment.

The following table illustrates a board operative range of ingredients and also a preferred or optimum composition of our colored liquid penetrant.

In the above table, the methyl ester of a fatty acid is readily biodegradable. Satisfactory embodiments thereof are available under the names Methyl Lardate Base ML; Methyl Sperm; and Methyl Sperm 40. In general, suitable methyl esters are those of fatty acids of between 16 and 24 C-atoms, and, preferably, fatty acids derivable from lard having from 16 to 18 (both inclusive) C-atoms. The following are typical specifications of methyl esters that are satisfactory for our use as the principal liquid component of our penetrant composition. These esters are not employed as surfactants but as solvents for the dye.

METHYL ESTERS Typical Specifications W .Base ML V Viscosity at 100 F. (SUS) 47 Pour Point (ASTM) 50 max. Color (ASTM) 1 max. Sap. No. 185-195 Iodine No. 55-65 Flash Point 325-350 F. Acid No. .5 max. Free Alcohol none Surface Tension (Dynes) 28 lbs. gal. at 60 F. 7.35 MIU 1% max.

Methyl Sperm 40 is a mixture of methyl esters but differs in many respects from the foregoing. Methyl Sperm 40 contains about one-third methyl esters of fatty acids and two-thirds fatty alcohol esters of fatty acids. The natural product 45 NW Sperm Oil contains one-third triglycerides and two-thirds fatty alcohol esters. The triglycerides portion is converted to methyl esters and the glycerine removed.

Methyl Sperm will not oxidize, does not polymerize, is miscible with petroleum oils, and most solvents. Also it does not decompose and is not volatile.

Typical Analysis Specifications Cloud point F. 43 42-45F. Pour Point F. 36F. Iii-40F. Acid No. 0.89 2.0 max. Free Fatty Acid as Oleic .45 1.0 max. Saponification value 133.0 129-136 Iodine value 78.8 74-85 Viscosity SSU at 100 F. 70.0 68-73 (50-70) SSU at 210 F. 41.5 40-43 Color- Gardner 6 8 max. Flash Point F. 415 410-425 Fire Point F. 440 435-450 Unsaponifiable 36% 33-39 Since Methyl Sperm does not contain glycerides, it has a lower viscosity than the fatty glycerides. The methyl esters act as oiliness agents and do not polymerize or form large molecules. Methyl Sperm 40 will emulsify more readily than sperm oil so is easier to convert to stable water base emulsions.

Considering only the fatty acid components that are usually present in sperm oil, these are largely palmitic with some myristic and stearic acids, and perhaps others, but all within the range of from 14 to 22 C- atoms. The fatty alcohol components in the sperm oil that are carried over in the refining step to form Methyl Sperm 40 are predominantly cetyl alcohol (16 C, saturated), oleyl alcohol (18 C, unsaturated) and arachidyl (20 C-, saturated). The released fatty acids are converted into their methyl esters, which then constitute what is termed Methyl Sperm 40.

Examples of nonionic surfactants that are readily biodegradable are the following:

l. A series of nonionics consisting of ethoxylates of isomeric secondary linear alcohols.

The linear alkyl hydrophobic portion is a mixture of C -C linear chains. The hydrophylic portion is a polyoxyethylene chain randomly attached to the linear aliphatic chain through an ether (-O) linkage.

Both the linear alcohol hydrophobic portion and the polyoxyethylene portion are capable of being effectively consumed by microorganisms.

Mixtures of these nonionics of differing molecular weights that are water soluble and non-gel forming, such as the following are preferred:

TYPICAL PHYSICAL AND CHEMICAL PROPERTIES DETERMINED ON TYPICAL COMMERCIAL MATERIAL Nonionics Property 15-S-5 l5-S-7 l5-S-9 15-S-l 2 Molecular Weight 420 508 596 728 Active Content 100 100 100 100 by Wt. Cloud point, 1.0% (a) 37 60 aqueous soL, C. Pour Point, C. -15 7 13 17 (+5F.) (45F.) (55F.) 63F.) Solubility in Soluble Soluble Soluble Soluble H O at 25 C. (c) Apparent Specific 0.970 0.994 1.006 1.023 Gravity, 20/20 C. LbJgal. 20 C. 8.07 8.26 8.37 8.49

Viscosity, cks. at 20 C. 51 67 86 120 40 C. 22.5 27 36 48 C. 3.8(b) 5.9 7.1 24 HLB Number (a) 12.8 13.8 15.0 Flash Point, F., Cleveland open cup 410 440 470 460 ASTM method D 92 (a) Not applicable (b) Extrapolated (c) With gel formation 2. A series of nonionic surfactants that are reaction products or adducts of ethylene oxide with nonyl or octyl phenol in a molar ratio of at least 10 to 1, with the average length of the hydrophylic polyoxyethylene chain preferably 12 oxyethylene (-OCI-I CI-I units.

These adducts are not preferred since the presence of the benzene ring renders them less easily biodegradable than the ethoxylated alcohols of paragraph 1 above; but if the side chain contains at least 6 oxyethylene units it is considered to be biodegradable.

With regard to the coupler shown in table 1, suitable couplers are the glycol-type, such as dipropylene or other alkylene glycol, glycol ethers and lower molecular weight polyethylene glycols. Alternatively, benzyl alcohol can be used as a coupler, but a coupler is not necessary; it is merely optional.

As for fluorescent dyes, any of the following are satisfactory:

Fluorol 7GA (Brightener No. 75)

Fluorol SGA (Brightener No. 74; C1 45,550)

4N Butylamino 1, 8-naphthal N-butylimide 4 Methyl 7 diethyl amino coumarin 4 Amino sulfo l, 8, naphthal 4 methyl phenylimide Calcofluor White U.L.A. Super Conc.

The above fluorescent dyes are oil-soluble and are soluble in the liquid vehicle comprising the methyl ester of a fatty acid and the nonionic surfactant set forth in table I. In general the fluorescent dyes can be used in the penetrant composition within the limits from about 0.1 percent up to 40 percent by weight, de pending on their respective solubilities in the liquid penetrant vehicle used. The abbreviation q.s. means a sufficient quantity, namely a quantity that is sufficient to give a color indication at the locus of a surface discontinuity that is rendered visible when viewed under the proper lighting. In the case of a fluorescent dye, inspection should be under black light, which provides a filtered ultraviolet radiation.

In employing any of the water washable, non-gelforming colored liquid penetrant compositions of our invention, the surface of the workpiece to be inspected is suitably prepared, as by cleaning, and the liquid penetrant composition is then applied to it as by brush coating, sprayings, dipping or immersing. The surface undergoing inspection is referred to as a solid" surface to distinguish from porous surfaces that are easily permeable by liquids to considerable depths, such as unfired ceramic articles. After application of an excess of the penetrant composition, sufficient time is allowed for penetration of the liquid composition into any surface discontinuities, flaws or the like, that may be present in the surface undergoing test. The excess penetrant is thereafter washed from the surface of the body, preferably by a scrubbing spray of water directed obliquely toward the surface of the article so as to wash off the excess of the penetrant without, however, washing entrapped penetrant, or penetrant residues, out of flaws that are open to the surface. The flaw indications may then be developed with any suitable type of known developer, such as a dry developer, or a wet developer, either of the aqueous or non-aqueous type. Thereafter, the treated surface is inspected under fluorescigenous lighting, whereupon the fluorescence of the penetrant retained in the flaws and appearing at the surface openings will afford visible indications of the locations of such flaws.

As previously stated herein, our colored liquid penetrant composition is water-washable without gel formation. In addition to its desirable readily biodegradable property, the liquid penetrant composition of our invention has a high degree of sensitivity and of brightness of indications; and the excess penetrant may be removed by rinsing or by an air-water spray using water within the temperature range of from 40 to 100 F. The penetrant freezes at about 6 C., turning into a waxy solid, but when brought back to higher temperatures, the penetrant composition returns to its normal liquid state without separation into layers.

While a development step has been included in the description of the method of using our colored liquid penetrant composition, the composition may be satisfactorily used without application of a developer since the indications after washing form instantaneously. It is nevertheless advantageous to use a developer, where the defects are tightly grouped, in order to freeze the indications and thereby promote a high degree of resolution by preventing over-development. Removal of excess of the penetrant composition from the surface undergoing testing can be effected by gentle rinsing or by forceful water spray carried out in such a manner as to free the background from excessive fluorescent residue, which would mask fine indications.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. A liquid penetrant testing composition for the detection of surface discontinuities in work pieces, consisting essentially of a major amount of a methyl ester of a fatty acid containing between 16 and 24 C-atoms, a minor amount of a nonionic, biodegradable, watersoluble surfactant and a fluorescent dye dissolved therein, the resultant liquid penetrant composition being water washable and non-gel-forming upon the addition of water, said surfactant being selected from the group consisting of polyethoxylates of l secondary linear alcohols having a hydrophobic carbon chain of 13 to 17 C-atoms and (2) phenols selected from the group consisting of nonyl and octyl phenol, and said dye being present in a quantity sufficient to give color indication at said surface discontinuities when excess penetrant composition is water-washed from the work pieces, group (1) containing 8 or 9 oxyethylene and group (2) containing at least 10 oxyethylene units per molecule.

2. A composition as defined by claim 1, wherein methyl ester is an ester of fatty acids contained in lard.

3. A composition as defined in claim 1, wherein said methyl ester is a methyl ester of a fatty acid having from 16 to 18 C-atoms, both inclusive, said methyl ester having a viscosity at 100 F. (SUS) of approximately 47, a flash point of from 325 to 350 F. and a surface tension of about 28 dynes.

4. A composition as defined in claim 1, wherein said composition has the following ingredients within the ranges of parts by weight that are indicated:

Ingredient Parts by weight nonionic surfactant 7 to 30 methyl ester ofa fatty acid 50 to 75 fluorescent dye q.s.

5. A composition as defined in claim 1, wherein said composition has the following ingredients in approximately the parts by weight indicated:

Ingredient Parts by Weight nonionic surfactant 25 methyl ester of a C ,C fatty acid a glycol coupler 5 fluorescent dye q.s.

6. A composition as defined in claim 4, wherein said nonionic surfactant is a mixture of ethoxylates of isomeric secondary linear alcohols.

7. A composition in accordance with claim in which the nonionic surfactant is a mixture of polyethoxylates of isomeric secondary linear alcohols. 

1. A liquid penetrant testing composition for the detection of surface discontinuities in work pieces, consisting essentially of a major amount of a methyl ester of a fatty acid containing between 16 and 24 C-atoms, a minor amount of a nonionic, biodegradable, water-soluble surfactant and a fluorescent dye dissolved therein, the resultant liquid penetrant composition being water washable and non-gel-forming upon the addition of water, said surfactant being selected from the group consisting of polyethoxylates of (1) secondary linear alcohols having a hydrophobic carbon chain of 13 to 17 C-atoms and (2) phenols selected from the group consisting of nonyl and octyl phenol, and said dye being present in a quantity sufficient to give color indication at said surface discontinuities when excess penetrant composition is water-washed from the work pieces, group (1) containing 8 or 9 oxyethylene and group (2) containing at least 10 oxyethylene units per molecule.
 2. A composition as defined by claim 1, wherein methyl ester is an ester of fatty acids contained in lard.
 3. A composition as defined in claim 1, wherein said methyl ester is a methyl ester of a fatty acid having from 16 to 18 C-atoms, both inclusive, said methyl ester having a viscosity at 100* F. (SUS) of approximately 47, a flash point of from 325* to 350* F. and a surface tension of about 28 dynes.
 4. A composition as defined in claim 1, wherein said composition has the following ingredients within the ranges of parts by weight that are indicated: Ingredient Parts by weight nonionic surfactant 7 to 30 methyl ester of a fatty acid 50 to 75 fluorescent dye q.s.
 5. A composition as defined in claim 1, wherein said composition has the following ingredients in approximately the parts by weight indicated: Ingredient Parts by Weight nonionic surfactant 25 methyl ester of a C16-C24 70 fatty acid a glycol coupler 5 fluorescent dye q.s.
 6. A composition as defined in claim 4, wherein said nonionic surfactant is a mixture of ethoxylates of isomeric secondary linear alcohols. 